<html>
<head>
<script>
</script>
</head>
<body >
<div id='d1' data-sub='abc123' data-sub-sub='efg456' >data-sub='abc123' data-sub-sub='efg456'</div>
<button onclick="alert( document.getElementById('d1').dataset.sub )" >dataset.sub</button>
<button onclick="alert( document.getElementById('d1').dataset.subSub )" >dataset.sub.sub</button>
</body>
</html>
